Meat Safety Part 2 Dr Mohamed Abdelfattah Maky

Meat Safety Part 2 Dr. Mohamed Abdelfattah Maky Food Hygiene Department

3 - Nutrient content o. Categories o. Sources of energy § Growth factors: a. purine and pyrimidine b. Amino acids c. Vitamins

Microorganisms require certain basic nutrients for growth and maintenance of metabolic functions. The amount and type of nutrients required range widely depending on the microorganisms. These nutrients include water, a source of energy, nitrogen, vitamins, and minerals. Varying amounts of these nutrients are present in meat. Meat have abundant protein, lipids, minerals and vitamins. Most muscle foods have low levels of carbohydrates

Growth factors are required in small amounts by bacteria because they fulfill specific roles in biosynthesis. The need for a growth factor results from either a blocked or missing metabolic pathway in the cells. Growth factors are organized into three categories: 1 -Purines and pyrimidines: required for synthesis of nucleic acid. 2 -Amino acids: required for the synthesis of proteins 3 -Vitamins: needed as coenzymes and functional groups of certain enzymes. Some bacteria as E. coli do not require any growth factors; they can synthesis all essential purines, pyrimidines, amino acids and vitamins, starting with their carbon source , as part of their own intermediary metabolism. Some minerals required for microbial growth include phosphorus, iron, magnesium, sulfur, manganese, calcium and potassium. In general, small amounts of these minerals are required, thus meat can serve as good sources of minerals.

4 -Biological structure Meat (carcass) in the raw state, have biological structure (superficial fascia and fat) that may prevent the penetration and growth of pathogenic microorganisms. Meat may have pathogenic microorganisms attached to the surface or trapped within surface folds

Several factors may influence penetration of these barriers 1. Physical damage due to un-necessary incisions, transport, or storage, as well as invasion of insects can allow the penetration of microorganisms. 2. During the meat processing such as slicing, chopping, and gridding , will destroy the physical barriers. Thus, the interior of food can become contaminated and growth can occur. 3. Meat cooking also break down protective biological structures and alter such factors as p. H and aw. These changes could potentially allow the growth of microbial pathogens.

Redox potential /oxidation-reduction potential Def Eh Measured: m. V +810 m. V / - 420 m. V at p. H 7. 0, 30 C

Definition: The oxidation –reduction or redox potential of a substance is defined in terms of the ratio of the total oxidizing (electron accepting) power to the total reducing (electron donating) power of the substance. In effect, redox potential is a measurement of the ease by which a substance gains or loses electrons. Eh defines whether a system is oxidizing or reducing in character The redox potential (Eh) is measured in terms of millivolts.

Eh Value for some meat Food item Presence of air Eh (m. V) p. H Meat Raw, post-rigor - -60 to -150 5. 7 minced + +225 5. 9

Vacuum packaging The vacuum packaging is packaging associated with an exhaust gas and thus a reduction of oxygen in the environment of the product. It allows you to remove the adverse effects caused by the presence of oxygen. Modified atmosphere packaging In contrast to the vacuum packaging, modified atmosphere packaging, also known as modified atmosphere packaging, is to change the environment of the gas produced by a reinjection of gases such as CO 2 and nitrogen.

Temperature

Microorganisms have been found growing in virtually all environments where there is liquid water, regardless of its temperature. All microorganisms have a defined temperature range in which they grow, with a minimum, maximum, and optimum. Temperature has dramatic impact on both generation time of an organism and its lag period.

Groups of microorganisms based on their temperature ranges for growth Group Temperature C Minimum Optimum Maximum Thermophiles 40 - 45 55 - 75 60 - 90 Mesophiles 5 - 15 30 - 45 35 - 47 Psychrophiles -5 - +5 12 - 15 15 - 20 Psychrotrophs -5 - +5 25 - 30 30 - 35

At low temperature, two factors govern the point at which growth stops: 1. Reaction rates for the individual enzymes in the organism become much slower. 2. Low temperature reduce the fluidity of the cytoplasmic membrane, thus interfering with transport mechanisms. At high temperature, structural cell components become denatured and inactivation of heat-sensitive enzymes occurs. While the growth rate increases with increasing tempertature

Time

Time is a critical consideration in growth rates of microbial pathogens, meat producers or manufacturers address the concept of time as it relates to microbial growth when a product shelf life is determined.

Shelf life is the time period from when the product is produced until the time it is intended to be consumed or used. several factors are used to determined a product shelf life, ranging from organoleptic qualities to microbiological safety. Time alone at ambient temperature can be used to control product safety. When time alone is used as control, the duration should be equal to or less than the lag phase of the pathogen (s) of concern in the product in q

Storage condition Meat Refrigerator Beef (fresh) Veal (fresh) Pork (fresh) Lamb (fresh) Sausage 2 to 4 days 1 week Freezer 6 to 12 months 6 to 9 months 3 to 6 months 6 to 9 months 60 days

Several factors effect on storage conditions of meat as temperature, the relative humidity and packaging material. When considering growth rate of microbial pathogens in meat, time and temperature are integral and must be considered together. Increase in storage and / or display temperature will decrease the shelf life of refrigerated meat since the higher the temperature , the more permissive conditions for growth.